diff --git a/.cargo/config.in b/.cargo/config.in
index 5dad42b6104e..e47e7a69c3c5 100644
--- a/.cargo/config.in
+++ b/.cargo/config.in
@@ -65,7 +65,7 @@ rev = "21c26326f5f45f415c49eac4ba5bc41a2f961321"
 [source."https://github.com/kinetiknz/audioipc-2"]
 git = "https://github.com/kinetiknz/audioipc-2"
 replace-with = "vendored-sources"
-rev = "499b95580c8b276e52bd9757d735249504202e5c"
+rev = "ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb"
 
 [source."https://github.com/jfkthame/mapped_hyph.git"]
 git = "https://github.com/jfkthame/mapped_hyph.git"
diff --git a/Cargo.lock b/Cargo.lock
index 3bd936c28dc7..cde03d2d38b3 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -318,7 +318,7 @@ dependencies = [
 [[package]]
 name = "audioipc2"
 version = "0.5.0"
-source = "git+https://github.com/kinetiknz/audioipc-2?rev=499b95580c8b276e52bd9757d735249504202e5c#499b95580c8b276e52bd9757d735249504202e5c"
+source = "git+https://github.com/kinetiknz/audioipc-2?rev=ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb#ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb"
 dependencies = [
  "arrayvec",
  "ashmem",
@@ -327,6 +327,7 @@ dependencies = [
  "byteorder",
  "bytes 1.2.1",
  "cc",
+ "crossbeam-channel",
  "cubeb",
  "error-chain",
  "iovec",
@@ -345,7 +346,7 @@ dependencies = [
 [[package]]
 name = "audioipc2-client"
 version = "0.5.0"
-source = "git+https://github.com/kinetiknz/audioipc-2?rev=499b95580c8b276e52bd9757d735249504202e5c#499b95580c8b276e52bd9757d735249504202e5c"
+source = "git+https://github.com/kinetiknz/audioipc-2?rev=ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb#ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb"
 dependencies = [
  "audio_thread_priority",
  "audioipc2",
@@ -356,7 +357,7 @@ dependencies = [
 [[package]]
 name = "audioipc2-server"
 version = "0.5.0"
-source = "git+https://github.com/kinetiknz/audioipc-2?rev=499b95580c8b276e52bd9757d735249504202e5c#499b95580c8b276e52bd9757d735249504202e5c"
+source = "git+https://github.com/kinetiknz/audioipc-2?rev=ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb#ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb"
 dependencies = [
  "audio_thread_priority",
  "audioipc2",
diff --git a/third_party/rust/audioipc2-client/.cargo-checksum.json b/third_party/rust/audioipc2-client/.cargo-checksum.json
index ed7ee847feee..44172d352965 100644
--- a/third_party/rust/audioipc2-client/.cargo-checksum.json
+++ b/third_party/rust/audioipc2-client/.cargo-checksum.json
@@ -1 +1 @@
-{"files":{"Cargo.toml":"31dc34fae9951183eaed3511cffe3d830d52ba3c046257454f09a06156d0716b","cbindgen.toml":"fb6abe1671497f432a06e40b1db7ed7cd2cceecbd9a2382193ad7534e8855e34","src/context.rs":"17bdf1dfc8d910b745f94d5bc74121850174c716f8a2eb6d1c4b075d42fa5df5","src/lib.rs":"c4a6797734489280f6b97dd72c9e51a7bd7be4104592eece3929e29d45cbca4a","src/send_recv.rs":"064a657c845762be1dbcbbfc18b3f8a51582eb540def8d2ceecf200184ad4f7a","src/stream.rs":"a6c07796e6fe704cfa6baf8b904e7ffe874d3c884d44d4ed307e668dec25452b"},"package":null}
\ No newline at end of file
+{"files":{"Cargo.toml":"31dc34fae9951183eaed3511cffe3d830d52ba3c046257454f09a06156d0716b","cbindgen.toml":"fb6abe1671497f432a06e40b1db7ed7cd2cceecbd9a2382193ad7534e8855e34","src/context.rs":"4593aa41ee97b72622b572ad80f0e4c939d8be2ea45fed1f5587f5a109a67735","src/lib.rs":"c4a6797734489280f6b97dd72c9e51a7bd7be4104592eece3929e29d45cbca4a","src/send_recv.rs":"859abe75b521eb4297c84b30423814b5b87f3c7741ad16fe72189212e123e1ac","src/stream.rs":"a6c07796e6fe704cfa6baf8b904e7ffe874d3c884d44d4ed307e668dec25452b"},"package":null}
\ No newline at end of file
diff --git a/third_party/rust/audioipc2-client/src/context.rs b/third_party/rust/audioipc2-client/src/context.rs
index 1e3d7fe7cbea..dc22159a257c 100644
--- a/third_party/rust/audioipc2-client/src/context.rs
+++ b/third_party/rust/audioipc2-client/src/context.rs
@@ -71,8 +71,7 @@ fn promote_thread(rpc: &rpccore::Proxy<ServerMessage, ClientMessage>) {
     match get_current_thread_info() {
         Ok(info) => {
             let bytes = info.serialize();
-            // Don't wait for the response, this is on the callback thread, which must not block.
-            rpc.call(ServerMessage::PromoteThreadToRealTime(bytes));
+            let _ = rpc.call(ServerMessage::PromoteThreadToRealTime(bytes));
         }
         Err(_) => {
             warn!("Could not remotely promote thread to RT.");
diff --git a/third_party/rust/audioipc2-client/src/send_recv.rs b/third_party/rust/audioipc2-client/src/send_recv.rs
index b0d41aca2ce1..1134c99a4996 100644
--- a/third_party/rust/audioipc2-client/src/send_recv.rs
+++ b/third_party/rust/audioipc2-client/src/send_recv.rs
@@ -43,7 +43,7 @@ macro_rules! send_recv {
         $rpc.call(ServerMessage::$smsg($($a),*))
     });
     (__recv $resp:expr, $rmsg:ident) => ({
-        match $resp.wait() {
+        match $resp {
             Ok(ClientMessage::$rmsg) => Ok(()),
             Ok(ClientMessage::Error(e)) => Err($crate::send_recv::_err(e)),
             Ok(m) => {
@@ -57,7 +57,7 @@ macro_rules! send_recv {
         }
     });
     (__recv $resp:expr, $rmsg:ident __result) => ({
-        match $resp.wait() {
+        match $resp {
             Ok(ClientMessage::$rmsg(v)) => Ok(v),
             Ok(ClientMessage::Error(e)) => Err($crate::send_recv::_err(e)),
             Ok(m) => {
diff --git a/third_party/rust/audioipc2-server/.cargo-checksum.json b/third_party/rust/audioipc2-server/.cargo-checksum.json
index 4b28668ef946..c474de6303b9 100644
--- a/third_party/rust/audioipc2-server/.cargo-checksum.json
+++ b/third_party/rust/audioipc2-server/.cargo-checksum.json
@@ -1 +1 @@
-{"files":{"Cargo.toml":"7feb495b23148ecc83ec7f480aefe19c9804a8900cdb4ceb005c049cdce82428","cbindgen.toml":"fb6abe1671497f432a06e40b1db7ed7cd2cceecbd9a2382193ad7534e8855e34","src/lib.rs":"d9cc7ca311cceb70acbc63b2190d6205094152e582faaad1b4a6061019f5803f","src/server.rs":"00740854f3e4f64cbeabfdb04d1337a2fdb89122464ea64d23fe1272045aee7d"},"package":null}
\ No newline at end of file
+{"files":{"Cargo.toml":"7feb495b23148ecc83ec7f480aefe19c9804a8900cdb4ceb005c049cdce82428","cbindgen.toml":"fb6abe1671497f432a06e40b1db7ed7cd2cceecbd9a2382193ad7534e8855e34","src/lib.rs":"d9cc7ca311cceb70acbc63b2190d6205094152e582faaad1b4a6061019f5803f","src/server.rs":"362ec34c541e43befb95204795622b5a2da036f8e417d524c64eb6c6550d094b"},"package":null}
\ No newline at end of file
diff --git a/third_party/rust/audioipc2-server/src/server.rs b/third_party/rust/audioipc2-server/src/server.rs
index 9533af22dc64..d715c64aada3 100644
--- a/third_party/rust/audioipc2-server/src/server.rs
+++ b/third_party/rust/audioipc2-server/src/server.rs
@@ -252,14 +252,11 @@ impl ServerStreamCallbacks {
             return cubeb::ffi::CUBEB_ERROR.try_into().unwrap();
         }
 
-        let r = self
-            .data_callback_rpc
-            .call(CallbackReq::Data {
-                nframes,
-                input_frame_size: self.input_frame_size as usize,
-                output_frame_size: self.output_frame_size as usize,
-            })
-            .wait();
+        let r = self.data_callback_rpc.call(CallbackReq::Data {
+            nframes,
+            input_frame_size: self.input_frame_size as usize,
+            output_frame_size: self.output_frame_size as usize,
+        });
 
         match r {
             Ok(CallbackResp::Data(frames)) => {
@@ -282,8 +279,7 @@ impl ServerStreamCallbacks {
         trace!("Stream state callback: {:?}", state);
         let r = self
             .state_callback_rpc
-            .call(CallbackReq::State(state.into()))
-            .wait();
+            .call(CallbackReq::State(state.into()));
         match r {
             Ok(CallbackResp::State) => {}
             _ => {
@@ -296,8 +292,7 @@ impl ServerStreamCallbacks {
         trace!("Stream device change callback");
         let r = self
             .device_change_callback_rpc
-            .call(CallbackReq::DeviceChange)
-            .wait();
+            .call(CallbackReq::DeviceChange);
         match r {
             Ok(CallbackResp::DeviceChange) => {}
             _ => {
@@ -347,8 +342,7 @@ impl DeviceCollectionChangeCallback {
         );
         let _ = self
             .rpc
-            .call(DeviceCollectionReq::DeviceChange(device_type))
-            .wait();
+            .call(DeviceCollectionReq::DeviceChange(device_type));
     }
 }
 
diff --git a/third_party/rust/audioipc2/.cargo-checksum.json b/third_party/rust/audioipc2/.cargo-checksum.json
index 82f0db292104..8098377aeaff 100644
--- a/third_party/rust/audioipc2/.cargo-checksum.json
+++ b/third_party/rust/audioipc2/.cargo-checksum.json
@@ -1 +1 @@
-{"files":{"Cargo.toml":"4a6aaffaf15fc11d3c41fc399a6e36a1ac9016f0edd592d4ff4059a2092818af","benches/serialization.rs":"d56855d868dab6aa22c8b03a61084535351b76c94b68d8b1d20764e352fe473f","build.rs":"65df9a97c6cdaa3faf72581f04ac289197b0b1797d69d22c1796e957ff1089e2","src/codec.rs":"4e029396765db803201249e90bcf724eb56deed3b2e455822d6673f40550a3e1","src/errors.rs":"67a4a994d0724397657581cde153bdfc05ce86e7efc467f23fafc8f64df80fa4","src/ipccore.rs":"6d33898f5bc61963797d21b44d36a7ee52d3d0cf13a4f19fa2d59373720eead8","src/lib.rs":"9b107cb52081eeea3fa742d30361db70f7138baa423dfe21d37dcf5087afc338","src/messages.rs":"452362da2cace9a0f2e3134c190ecb6a9997f8be4036cde06643e17c6c238240","src/rpccore.rs":"9fa24cb6d487b436382e35f82d0809ad2b315ce049ebaa767b4f88d3d5637f2e","src/shm.rs":"1d88f19606899e3e477865d6b84bbe3e272f51618a1c2d57b6dab03a4787cde3","src/sys/mod.rs":"e6fa1d260abf093e1f7b50185195e2d3aee0eb8c9774c6f253953b5896d838f3","src/sys/unix/cmsg.rs":"8a27a20383c333c5d033e58a546a530e26b964942a4615793d1ca078c65efb75","src/sys/unix/cmsghdr.c":"d7344b3dc15cdce410c68669b848bb81f7fe36362cd3699668cb613fa05180f8","src/sys/unix/mod.rs":"59835f0d5509940078b1820a54f49fc5514adeb3e45e7d21e3ab917431da2e74","src/sys/unix/msg.rs":"c0103cc058aeb890ab7aa023fcd6d3b9a0135d6b28fdecdec446650957210508","src/sys/windows/mod.rs":"7b1288e42b3ce34c7004b9fe3eeb6d9822c55e2688d3c2a40e55db46a2ca5d76"},"package":null}
\ No newline at end of file
+{"files":{"Cargo.toml":"8b2d3abbe023360a24d37b306dbec9e8bd0162025d38ca106ebcc8d7abab4039","benches/serialization.rs":"d56855d868dab6aa22c8b03a61084535351b76c94b68d8b1d20764e352fe473f","build.rs":"65df9a97c6cdaa3faf72581f04ac289197b0b1797d69d22c1796e957ff1089e2","src/codec.rs":"4e029396765db803201249e90bcf724eb56deed3b2e455822d6673f40550a3e1","src/errors.rs":"67a4a994d0724397657581cde153bdfc05ce86e7efc467f23fafc8f64df80fa4","src/ipccore.rs":"eda3629e363124c84d5b826dea03f5551a8adad6c8efbc61b98f7d6572fdfa18","src/lib.rs":"9b107cb52081eeea3fa742d30361db70f7138baa423dfe21d37dcf5087afc338","src/messages.rs":"452362da2cace9a0f2e3134c190ecb6a9997f8be4036cde06643e17c6c238240","src/rpccore.rs":"21568946ca59e0cf1cb0dc6254ebda577a014343438a4fde2556a22e44eea2bf","src/shm.rs":"1d88f19606899e3e477865d6b84bbe3e272f51618a1c2d57b6dab03a4787cde3","src/sys/mod.rs":"e6fa1d260abf093e1f7b50185195e2d3aee0eb8c9774c6f253953b5896d838f3","src/sys/unix/cmsg.rs":"8a27a20383c333c5d033e58a546a530e26b964942a4615793d1ca078c65efb75","src/sys/unix/cmsghdr.c":"d7344b3dc15cdce410c68669b848bb81f7fe36362cd3699668cb613fa05180f8","src/sys/unix/mod.rs":"59835f0d5509940078b1820a54f49fc5514adeb3e45e7d21e3ab917431da2e74","src/sys/unix/msg.rs":"c0103cc058aeb890ab7aa023fcd6d3b9a0135d6b28fdecdec446650957210508","src/sys/windows/mod.rs":"7b1288e42b3ce34c7004b9fe3eeb6d9822c55e2688d3c2a40e55db46a2ca5d76"},"package":null}
\ No newline at end of file
diff --git a/third_party/rust/audioipc2/Cargo.toml b/third_party/rust/audioipc2/Cargo.toml
index 13a92b196ac5..17ef5b94e844 100644
--- a/third_party/rust/audioipc2/Cargo.toml
+++ b/third_party/rust/audioipc2/Cargo.toml
@@ -21,6 +21,7 @@ serde_bytes = "0.11"
 mio = { version = "0.8",  features = ["os-poll", "net", "os-ext"] }
 slab = "0.4"
 scopeguard = "1.1.0"
+crossbeam-channel = "0.5"
 
 [target.'cfg(unix)'.dependencies]
 iovec = "0.1"
diff --git a/third_party/rust/audioipc2/src/ipccore.rs b/third_party/rust/audioipc2/src/ipccore.rs
index bfed10a42a87..6e607db2e89b 100644
--- a/third_party/rust/audioipc2/src/ipccore.rs
+++ b/third_party/rust/audioipc2/src/ipccore.rs
@@ -7,6 +7,7 @@ use std::io::{self, Result};
 use std::sync::{mpsc, Arc};
 use std::thread;
 
+use crossbeam_channel::{self, Receiver, Sender};
 use mio::{event::Event, Events, Interest, Poll, Registry, Token, Waker};
 use slab::Slab;
 
@@ -53,7 +54,7 @@ enum Request {
 #[derive(Clone, Debug)]
 pub struct EventLoopHandle {
     waker: Arc<Waker>,
-    requests_tx: mpsc::Sender<Request>,
+    requests_tx: Sender<Request>,
 }
 
 impl EventLoopHandle {
@@ -140,8 +141,8 @@ struct EventLoop {
     waker: Arc<Waker>,
     name: String,
     connections: Slab<Connection>,
-    requests_rx: mpsc::Receiver<Request>,
-    requests_tx: mpsc::Sender<Request>,
+    requests_rx: Receiver<Request>,
+    requests_tx: Sender<Request>,
 }
 
 const EVENT_LOOP_INITIAL_CLIENTS: usize = 64; // Initial client allocation, exceeding this will cause the connection slab to grow.
@@ -151,7 +152,7 @@ impl EventLoop {
     fn new(name: String) -> Result<EventLoop> {
         let poll = Poll::new()?;
         let waker = Arc::new(Waker::new(poll.registry(), WAKE_TOKEN)?);
-        let (tx, rx) = mpsc::channel();
+        let (tx, rx) = crossbeam_channel::bounded(EVENT_LOOP_INITIAL_CLIENTS);
         let eventloop = EventLoop {
             poll,
             events: Events::with_capacity(EVENT_LOOP_EVENTS_PER_ITERATION),
@@ -824,7 +825,7 @@ mod test {
 
         // RPC message from client to server.
         let response = client_proxy.call(TestServerMessage::TestRequest);
-        let response = response.wait().expect("client response");
+        let response = response.expect("client response");
         assert_eq!(response, TestClientMessage::TestResponse);
 
         // Explicit shutdown.
@@ -840,7 +841,7 @@ mod test {
 
         // RPC message from client to server.
         let response = client_proxy.call(TestServerMessage::TestRequest);
-        let response = response.wait().expect("client response");
+        let response = response.expect("client response");
         assert_eq!(response, TestClientMessage::TestResponse);
 
         // Explicit shutdown.
@@ -855,7 +856,7 @@ mod test {
         drop(server);
 
         let response = client_proxy.call(TestServerMessage::TestRequest);
-        response.wait().expect_err("sending on closed channel");
+        response.expect_err("sending on closed channel");
     }
 
     #[test]
@@ -865,7 +866,7 @@ mod test {
         drop(client);
 
         let response = client_proxy.call(TestServerMessage::TestRequest);
-        response.wait().expect_err("sending on a closed channel");
+        response.expect_err("sending on a closed channel");
     }
 
     #[test]
diff --git a/third_party/rust/audioipc2/src/rpccore.rs b/third_party/rust/audioipc2/src/rpccore.rs
index f208ba3b1f7d..bb0a0bc7fe01 100644
--- a/third_party/rust/audioipc2/src/rpccore.rs
+++ b/third_party/rust/audioipc2/src/rpccore.rs
@@ -3,11 +3,14 @@
 // This program is made available under an ISC-style license.  See the
 // accompanying file LICENSE for details
 
+use std::collections::VecDeque;
 use std::io::{self, Result};
 use std::mem::ManuallyDrop;
-use std::{collections::VecDeque, sync::mpsc};
+use std::sync::{Arc, Mutex, Weak};
 
+use crossbeam_channel::{self, Receiver, Sender};
 use mio::Token;
+use slab::Slab;
 
 use crate::ipccore::EventLoopHandle;
 
@@ -41,21 +44,57 @@ pub trait Server {
     fn process(&mut self, req: Self::ServerMessage) -> Self::ClientMessage;
 }
 
-// RPC Client Proxy implementation.  ProxyRequest's Sender is connected to ProxyReceiver's Receiver,
-// allowing the ProxyReceiver to wait on a response from the proxy.
-type ProxyRequest<Request, Response> = (Request, mpsc::Sender<Response>);
-type ProxyReceiver<Request, Response> = mpsc::Receiver<ProxyRequest<Request, Response>>;
+// RPC Client Proxy implementation.
+type ProxyKey = usize;
+type ProxyRequest<Request> = (ProxyKey, Request);
 
-// Each RPC Proxy `call` returns a blocking waitable ProxyResponse.
-// `wait` produces the response received over RPC from the associated
-// Proxy `call`.
-pub struct ProxyResponse<Response> {
-    inner: mpsc::Receiver<Response>,
+// RPC Proxy that may be `clone`d for use by multiple owners/threads.
+// A Proxy `call` arranges for the supplied request to be transmitted
+// to the associated Server via RPC and blocks awaiting the response
+// via `response_rx`.
+// A Proxy is associated with the ClientHandler via `handler_tx` to send requests,
+// `response_rx` to receive responses, and uses `key` to identify the Proxy with
+// the sending side of `response_rx`  ClientHandler.
+// Each Proxy is registered with the ClientHandler on initialization via the
+// ProxyManager and unregistered when dropped.
+// A ClientHandler normally lives until the last Proxy is dropped, but if the ClientHandler
+// encounters an internal error, `response_tx` will be closed and `proxy_mgr` can
+// no longer be upgraded to register new Proxies.
+#[derive(Debug)]
+pub struct Proxy<Request, Response> {
+    handle: Option<(EventLoopHandle, Token)>,
+    key: ProxyKey,
+    response_rx: Receiver<Response>,
+    handler_tx: ManuallyDrop<Sender<ProxyRequest<Request>>>,
+    proxy_mgr: Weak<ProxyManager<Response>>,
 }
 
-impl<Response> ProxyResponse<Response> {
-    pub fn wait(&self) -> Result<Response> {
-        match self.inner.recv() {
+impl<Request, Response> Proxy<Request, Response> {
+    fn new(
+        handler_tx: Sender<ProxyRequest<Request>>,
+        proxy_mgr: Weak<ProxyManager<Response>>,
+    ) -> Self {
+        let (tx, rx) = crossbeam_channel::bounded(1);
+        Self {
+            handle: None,
+            key: proxy_mgr.upgrade().unwrap().register_proxy(tx),
+            response_rx: rx,
+            handler_tx: ManuallyDrop::new(handler_tx),
+            proxy_mgr,
+        }
+    }
+
+    pub fn call(&self, request: Request) -> Result<Response> {
+        match self.handler_tx.send((self.key, request)) {
+            Ok(_) => self.wake_connection(),
+            Err(_) => {
+                return Err(std::io::Error::new(
+                    std::io::ErrorKind::Other,
+                    "proxy send error",
+                ))
+            }
+        }
+        match self.response_rx.recv() {
             Ok(resp) => Ok(resp),
             Err(_) => Err(std::io::Error::new(
                 std::io::ErrorKind::Other,
@@ -63,27 +102,6 @@ impl<Response> ProxyResponse<Response> {
             )),
         }
     }
-}
-
-// RPC Proxy that may be `clone`d for use by multiple owners/threads.
-// A Proxy `call` arranges for the supplied request to be transmitted
-// to the associated Server via RPC.  The response can be retrieved by
-// `wait`ing on the returned ProxyResponse.
-#[derive(Debug)]
-pub struct Proxy<Request, Response> {
-    handle: Option<(EventLoopHandle, Token)>,
-    tx: ManuallyDrop<mpsc::Sender<ProxyRequest<Request, Response>>>,
-}
-
-impl<Request, Response> Proxy<Request, Response> {
-    pub fn call(&self, request: Request) -> ProxyResponse<Response> {
-        let (tx, rx) = mpsc::channel();
-        match self.tx.send((request, tx)) {
-            Ok(_) => self.wake_connection(),
-            Err(e) => debug!("Proxy::call error={:?}", e),
-        }
-        ProxyResponse { inner: rx }
-    }
 
     pub(crate) fn connect_event_loop(&mut self, handle: EventLoopHandle, token: Token) {
         self.handle = Some((handle, token));
@@ -100,9 +118,13 @@ impl<Request, Response> Proxy<Request, Response> {
 
 impl<Request, Response> Clone for Proxy<Request, Response> {
     fn clone(&self) -> Self {
-        Proxy {
+        let (tx, rx) = crossbeam_channel::bounded(1);
+        Self {
             handle: self.handle.clone(),
-            tx: self.tx.clone(),
+            key: self.proxy_mgr.upgrade().unwrap().register_proxy(tx),
+            response_rx: rx,
+            handler_tx: self.handler_tx.clone(),
+            proxy_mgr: self.proxy_mgr.clone(),
         }
     }
 }
@@ -110,15 +132,56 @@ impl<Request, Response> Clone for Proxy<Request, Response> {
 impl<Request, Response> Drop for Proxy<Request, Response> {
     fn drop(&mut self) {
         trace!("Proxy drop, waking EventLoop");
+        if let Some(mgr) = self.proxy_mgr.upgrade() {
+            mgr.unregister_proxy(self.key)
+        }
         // Must drop Sender before waking the connection, otherwise
         // the wake may be processed before Sender is closed.
-        unsafe { ManuallyDrop::drop(&mut self.tx) }
+        unsafe {
+            ManuallyDrop::drop(&mut self.handler_tx);
+        }
         if self.handle.is_some() {
             self.wake_connection()
         }
     }
 }
 
+const RPC_CLIENT_INITIAL_PROXIES: usize = 32; // Initial proxy pre-allocation per client.
+
+// Manage the Sender side of a ClientHandler's Proxies.  Each Proxy registers itself with
+// the manager on initialization.
+#[derive(Debug)]
+struct ProxyManager<Response> {
+    proxies: Mutex<Slab<Sender<Response>>>,
+}
+
+impl<Response> ProxyManager<Response> {
+    fn new() -> Self {
+        Self {
+            proxies: Mutex::new(Slab::with_capacity(RPC_CLIENT_INITIAL_PROXIES)),
+        }
+    }
+
+    // Register a Proxy's response Sender, returning a unique ID identifying
+    // the Proxy to the ClientHandler.
+    fn register_proxy(&self, tx: Sender<Response>) -> ProxyKey {
+        let mut proxies = self.proxies.lock().unwrap();
+        let entry = proxies.vacant_entry();
+        let key = entry.key();
+        entry.insert(tx);
+        key
+    }
+
+    fn unregister_proxy(&self, key: ProxyKey) {
+        let _ = self.proxies.lock().unwrap().remove(key);
+    }
+
+    // Deliver ClientHandler's Response to the Proxy associated with `key`.
+    fn deliver(&self, key: ProxyKey, resp: Response) {
+        let _ = self.proxies.lock().unwrap()[key].send(resp);
+    }
+}
+
 // Client-specific Handler implementation.
 // The IPC EventLoop Driver calls this to execute client-specific
 // RPC handling.  Serialized messages sent via a Proxy are queued
@@ -127,8 +190,26 @@ impl<Request, Response> Drop for Proxy<Request, Response> {
 // trigger response completion by sending the response via a channel
 // connected to a ProxyResponse.
 pub(crate) struct ClientHandler<C: Client> {
-    messages: ProxyReceiver<C::ServerMessage, C::ClientMessage>,
-    in_flight: VecDeque<mpsc::Sender<C::ClientMessage>>,
+    messages: Receiver<ProxyRequest<C::ServerMessage>>,
+    // Proxies hold a Weak<ProxyManager> to register on initialization.
+    // When ClientHandler drops, any Proxies blocked on a response will
+    // error due to the Sender closing.
+    proxies: Arc<ProxyManager<C::ClientMessage>>,
+    in_flight: VecDeque<ProxyKey>,
+}
+
+impl<C: Client> ClientHandler<C> {
+    fn new(rx: Receiver<ProxyRequest<C::ServerMessage>>) -> ClientHandler<C> {
+        ClientHandler::<C> {
+            messages: rx,
+            proxies: Arc::new(ProxyManager::new()),
+            in_flight: VecDeque::with_capacity(RPC_CLIENT_INITIAL_PROXIES),
+        }
+    }
+
+    fn proxy_manager(&self) -> Weak<ProxyManager<<C as Client>::ClientMessage>> {
+        Arc::downgrade(&self.proxies)
+    }
 }
 
 impl<C: Client> Handler for ClientHandler<C> {
@@ -137,8 +218,9 @@ impl<C: Client> Handler for ClientHandler<C> {
 
     fn consume(&mut self, response: Self::In) -> Result<()> {
         trace!("ClientHandler::consume");
-        if let Some(complete) = self.in_flight.pop_front() {
-            drop(complete.send(response));
+        // `proxy` identifies the waiting Proxy expecting `response`.
+        if let Some(proxy) = self.in_flight.pop_front() {
+            self.proxies.deliver(proxy, response);
         } else {
             return Err(std::io::Error::new(
                 std::io::ErrorKind::Other,
@@ -154,12 +236,12 @@ impl<C: Client> Handler for ClientHandler<C> {
 
         // Try to get a new message
         match self.messages.try_recv() {
-            Ok((request, response_tx)) => {
+            Ok((proxy, request)) => {
                 trace!("  --> received request");
-                self.in_flight.push_back(response_tx);
+                self.in_flight.push_back(proxy);
                 Ok(Some(request))
             }
-            Err(mpsc::TryRecvError::Empty) => {
+            Err(crossbeam_channel::TryRecvError::Empty) => {
                 trace!("  --> no request");
                 Ok(None)
             }
@@ -173,19 +255,12 @@ impl<C: Client> Handler for ClientHandler<C> {
 
 pub(crate) fn make_client<C: Client>(
 ) -> (ClientHandler<C>, Proxy<C::ServerMessage, C::ClientMessage>) {
-    let (tx, rx) = mpsc::channel();
+    let (tx, rx) = crossbeam_channel::bounded(RPC_CLIENT_INITIAL_PROXIES);
 
-    let handler = ClientHandler::<C> {
-        messages: rx,
-        in_flight: VecDeque::with_capacity(32),
-    };
+    let handler = ClientHandler::new(rx);
+    let proxy_mgr = handler.proxy_manager();
 
-    let proxy = Proxy {
-        handle: None,
-        tx: ManuallyDrop::new(tx),
-    };
-
-    (handler, proxy)
+    (handler, Proxy::new(tx, proxy_mgr))
 }
 
 // Server-specific Handler implementation.
@@ -226,9 +301,11 @@ impl<S: Server> Handler for ServerHandler<S> {
     }
 }
 
+const RPC_SERVER_INITIAL_CLIENTS: usize = 32; // Initial client allocation per server.
+
 pub(crate) fn make_server<S: Server>(server: S) -> ServerHandler<S> {
     ServerHandler::<S> {
         server,
-        in_flight: VecDeque::with_capacity(32),
+        in_flight: VecDeque::with_capacity(RPC_SERVER_INITIAL_CLIENTS),
     }
 }
diff --git a/toolkit/library/rust/shared/Cargo.toml b/toolkit/library/rust/shared/Cargo.toml
index 994e545f8a58..e025de9e3eb3 100644
--- a/toolkit/library/rust/shared/Cargo.toml
+++ b/toolkit/library/rust/shared/Cargo.toml
@@ -25,8 +25,8 @@ webrender_bindings = { path = "../../../../gfx/webrender_bindings" }
 cubeb-coreaudio = { git = "https://github.com/mozilla/cubeb-coreaudio-rs", rev = "44eca95823bb57e964cf7b6d9791ed2ccb4b2108", optional = true }
 cubeb-pulse = { git = "https://github.com/mozilla/cubeb-pulse-rs", rev="1f1fe1e08e01a9a534ec7f079702a583a0899ce7", optional = true, features=["pulse-dlopen"] }
 cubeb-sys = { version = "0.10", optional = true, features=["gecko-in-tree"] }
-audioipc2-client = { git = "https://github.com/kinetiknz/audioipc-2", rev = "499b95580c8b276e52bd9757d735249504202e5c", optional = true } # macos (v2) branch
-audioipc2-server = { git = "https://github.com/kinetiknz/audioipc-2", rev = "499b95580c8b276e52bd9757d735249504202e5c", optional = true } # macos (v2) branch
+audioipc2-client = { git = "https://github.com/kinetiknz/audioipc-2", rev = "ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb", optional = true } # macos (v2) branch
+audioipc2-server = { git = "https://github.com/kinetiknz/audioipc-2", rev = "ea7cabf8c9dc051a52ffb6cd7d2564b29b7428eb", optional = true } # macos (v2) branch
 audioipc-client = { git = "https://github.com/mozilla/audioipc", rev = "fb7a2b12ced3b43e6a268621989c6191d1ed7e39", optional = true }
 audioipc-server = { git = "https://github.com/mozilla/audioipc", rev = "fb7a2b12ced3b43e6a268621989c6191d1ed7e39", optional = true }
 # Force tokio-reactor on an old version to avoid new dependencies of newer versions.